As in the title, make these 4 things happen = profit!
The more options the better. Let players decide which way they prefer by simply making these available. Adjust the prices of these to fit the cost of your xp scrolls and/or vice versa et voila happy community.
ESO's mmo competition has it all, why don't you? Transfer lessens any possible upcoming frustration because of server problems. Level 50 boost is welcome to anyone who just wants to spend the least time dealing with leveling up new characters (new players as well as veterans). CP 300 boost makes the same group of players able to straight jump into vet content. And class change is a must for everyone who wants to play his main as a different class without the need to relevel every single line again and again (collecting skyshards too. having these in mind, adjusting prices there is not impossible either, isn't it? ). Could also just add fully leveled craft skill lines as a buyable option on top. Heck you can even make bundles of these with any combination you like to lure new players in. You will also make a lot of players return in no time since most of these things have been asked by retired players who have had no way of returning to the game because no transfer, boost or class change option available to them.
You did a character transfer in the past, when console versions released (but that was a 1 time deal only for PC>Console). And you can do it again. Maybe even a copy system of characters of the account to put it on a different platform. Your options are near endless and I doubt it would cost you much effort or money to implement.
I'm willing to buy all of it and others are too! So... just do it ZOS?